Despite a large body of evidence that systolic hypertension is at least as great a predictor of morbidity and mortality as is diastolic, and despite the awareness that systolic hypertension becomes the most common form of blood pressure elevation with age, prospective clinical trials involving lowering of systolic blood pressure by treatment with antihypertensive drugs are very few indeed. Those trials and cross-sectional observations that are reported are frequently conflicting. This proposal describes a prospective multicenter clinical trial, involving 11 possible participating clinical centers, a coordinating center, and laboratory and electrocardiograph subcenters, aimed at enrolling 4200 elderly individuals with primarily systolic hypertension in a five year, prospective randomized placebo controlled double blind trial of antihypertensive agents (or placebos). The primary objective is to observe each qualifying volunteer for five years to see whether active treatment of systolic hypertension decreases the incidence of stroke significantly. Secondary end points to be compared are the effect on cardiovascular mortality, incidence of nonfatal myocardial infarcts, the effect of treatment on incidence of cognitive impairment and psychiatric morbidity, and the effect of treatment on incidence of renal failure and congestive heart failure. A pilot phase is included to demonstrate feasibility and to pretest all procedures. Potential participants will be identified by organized blood pressure screening efforts in groups in which there is a large proportion aged 60 and over. Those qualified by screening will be evaluated and, if qualified and willing to give informed consent, randomized and titrated on medication (active or placebo, depending on randomization allocation). Each will then be followed for five full years on maintenance. Evaluation, randomization, titration and maintenance will take place in the clinical facility of each clinical center. It is estimated that 12,000 individuals age 60 and over will have to be screened at each center to get 400 qualified volunteers for randomization. Intake period is estimated at 18 months.